Public-address system



Patented Sept. 13, 1927.

UNITED STATES iii-ii, if]

PATET OFFICE.

IBRUNSON s. MoCUTCHEN, or, NORTH PLAINE -EL D, NEW JERSEY,- nssIGNoR ToAMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION on NEW YORK. I

PUBLIC-ADDRESS SYSTEM.

Application filed December 12, 1925. Serial No. 75,116.

instances wherein a loud speaker might be; located at a considerabledistance from the platform this .acoustic delay in the air path of thespeech might cause a bad'blurrin or echo effect to a listener near theloud spea er. Accordingly it is one of the primary objects of thisinvention to introduce an electrical delay invthe circuit of the loudspeaker to compensate for the acoustic delay to the, speech existing inthe air path.- With such an arran ementthe listener will not receive thespeec from the horn in advance of the direct speech from the speakerwith the attendant bad effect, but will receive the Speech from the hornin the same phase with and at the same time as the direct speech fromthe speaker. The arrangements of the invention also rovide distinctadvantages from the stan point of flexibility of w location of the loudspeakers for with the arrangements of the invention the loud speakers mabelocated at much greater distances than eretofore from the speaker. Thegreater distance at which the loud speaker may be located tendsto-reduce the existence of singing in the apparatus and hence the loudspeakers may be 0 erated at higher volume levels. Adcordin y, thearrangements of the invention ten to reduce singing, allow increasedvolume in'the operation of the loud speakers, and also afior greaterflexibihty in their location. Other objects and tures of the inventionwill appear more fully from the detailed description thereof hereinrgiven. e invention ma be more fully understood .from- .the 0 owingdescription, to-

ther with the accompanying drawing, m 6 Figures 1 and 2 of which theinvent1on 5o iBillustrl-ted. In Fig. 1 is a circuit diagram of one formof the arrangements of the invention'andin 2 are shown details of theelectrical reta devlces. p

In Fi 1 is shown "a microphone, or transll mitter, which might,be'located at a platfea- - form or any desirable spot of an auditorium,

or grounds, on which an address or other message or musical compositionis to'be de- -l1vered. The microphone may be connected; to an amplifier2. The output circuit of the coamp llfier .is shown as circuit 3.Connected to circuit 3 is the circuit 5 leading 'tothe loud speaker 7which would be located at some distanec away from the microphone and seaker. If the distance from the mlcrop one at which the loud speaker 7is located is found to be great enough so "that an acoustic'dela in theair path will cause the direct speec to, arrive at this positionsufliciently later than the speech from. the loud speaker 7 to cause ablurring or echo e-' f feet, the delay network 6'will be inserted incircuit 5 to com ensate for this delay. In the case of a lou speaker,such as'A located in close proximity to the micro one-no such delaycircuit would be provi ed. The loudspeaker 4 might even be omitted ifdesired. Associated with; circuit 3 might be other circuits, such as thecircuit 8, leading to other loud speakers, such as 10, located atotherpositions on the grounds. A delay network, such as 9, mightbe'iound desirable in the circuit 8 if the loudspeaker L0. were locatedat a suflicientdistance from the speaker and microphone 1. In. Fig. 2 isshown a suitable type of delay network to .be utilized in the-loudspeaker circuits, such as 5 and 8. The delay networks consist of anumber of sections comprisin inductance and capacity in series. The in'vidual sections are shown between the dotted lines a, b. The delaynetworks, such as 6 and 9, comprise a variable number of these sections1 depending upon the amount of acoustic delay in the air path which theyare desired to compensate. 7 0

'While the arrangements of the invention have been illustrated incertain specific forms which are deemed desirable, it is understood thatthey are capable of embodiment 1n many other widely varied forms withoutdepartms 'from the spirit of the inventlon as define by the appendedclaims. J. a

What isclaimed is;

1. In a public -a'ddress systema trans mitter. circuit, a plurahty ofcucmtsassociated therewith including loud speakmgoreceivers --located atvarious distances m said transmitter, and delay networks m cer- 91 saidcincuita.

2. In a public address system a'circuit including a, transmitter, a loudspeaklng receiver in said circuit located in close proximity to saidtransmitter, a second circuit associated with said first circuit andincluding a. loud speaking receiver located at a relatively greaterdistance from said transmitter than said first loud speaking receiver,and electrical retarding means in said second circuit.

3. A circuit including a transmitter, an. amplifier and a loud speakinreceiver, said loud speaking receiver being coated in relatively closeroximity to sald transmitter, a second circuit associated with saidfirst C11- cuit and including aloud speaking receiver located at arelatively greater distance from said transmitter than said firstreceiver, and means in said second circuit to-so retard the currentstransmitted thereover that both of said loud speaking receivers willoperate in the same phase.

4. A circuit including a transmitter and a loud speaking receiver, saidloud speaking receiver being located at a distance from said transmitterso great that an appreciable difference will exist between the acousticdelay in the air path between said transmitter and said loud speakingreceiver and the electrical delay in said circuit interconnecting saidtransmitter and said loud speaking receiver, and means for introducingelectrical delay in said circuit to compensate for the acoustic delay inthe air ath.

In testimony whereof, I have signe my name to this specification this10th day of December, 1925. v

BRUNSON S. MGCUTCHEN.

